[Amps] FW: Transformer Question

[Matt]

On the Gonset, the line filter choke is on the low voltage DC return side of the diode bridge, I assume to reduce 60Hz ripple.    It is undamaged.   Are you referring to this choke for removal?    The 811H schematic shows L7 (which I don't see defined in the parts list) on the HV DC supply leading to the RF plate choke tagged L4.    I assume L7 in the 811H design serves the same purpose but places the choke on the HV side instead of the LV side.

Regarding the 1.4 x transformer voltage...   I am puzzled by this too, and I assume the replacement transformer specs for both are listed as peak-to-peak, and not RMS, since the literature for both amps indicates the full load plate voltage as 1500 VDC.   I guess I could at least call Peter Dahl and ask them to confirm this.    I'm not sure if I could get anyone at MFJ who would know.... 

KM5VI
Matt

-----Original Message-----
From: Colin Lamb [mailto:k7fm at teleport.com] 
Sent: Thursday, February 27, 2020 8:44 AM
To: Matt <maflukey at gmail.com>; amps at contesting.com
Subject: Re: [Amps] Transformer Question

The GSB-201 only uses 20uf.  The capacitors are in series so the capacitance is divided by 5.  The replacement choke is good.  Throw the choke away.  With a capacitor input, you will have 1.4 x the transformer value.  So you will have the same value as the other amplifier.  But, one thing you will need higher tuning capacitor voltage to stand the voltage increase.  

So, you would want a transformer about 1250 volts x 1.414.  That will give you the same voltage as a choke input.  To make up for the choke, you will have to use bigger filter caps.  

Maybe you should read a little more about capacitor input power supplies before buying one.  

73,  K7FM

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